1. Field of the Invention
The invention relates to a method for processing two different thermoplastic films in a thermoforming system, a thermoforming system set up for carrying out such a method, a film supply station for the thermoforming system, a film strip, a use for the film strip, and a laminated part produced therewith.
2. Description of the Related Art
It is generally known and, for example, in the sector of the automotive supply industry, it is frequently carried out on a daily basis to mold the surface of a spatial component by means of a film.
A common way to do this is the production of laminated parts. In the course of this, contour-formed parts are covered with a film. The film is unwound from a roll, fed to a thermoforming system, heated and subsequently thermoformed over the carrier part in a forming station, for example by using a vacuum. Thereby, laminating takes place. An example for this is disclosed in EP 1 521 669 B1.
An alternative way, which does not require carrier parts, is subsequent back injection of the film, which in practice is designated as film preforming.
During sequential production, thus the production of different molded parts with sequentially different requirements, for example in terms of the surface contour or the surface color, it is necessary to frequently change the film rolls because the films form the finally visible surface of the finished molding. Specifically in the automotive industry, many time-consuming roll changes are required because normally in the targeted sequential production, frequent changes in the component surface to be achieved are required.
Customary products in a motor vehicle can be found primarily in the interior, for example as dashboards, door panels, instrument panels, glove compartment, map pocket or cup holder, wherein this list is not to be understood as being complete.
In order to avoid many time-consuming film roll changes, no rolls are used, thus no film strip is used that is continuously unwound from the film roll. Instead, “blank cuts” are processed. This means nothing other than that the different film rolls are in each case separated. A blank cut, thus a piece of film, is separated from the film roll. At this point it should already be pointed out that a blank cut can be prepared not necessarily only by means of a cutting method, but in general by means of any separating method. However, in practice, cutting has emerged as the most common method. It is readily conceivable as an alternative to instead separate the blank cut from the film roll by means of punching, shearing or flame-cutting or in any other way. What is important is that a blank cut is obtained, thus such a piece of film, which is needed for the upcoming processing flow through the thermoforming system.
The size of the blank cut is normally kept as small as possible simply for cost reduction and environmental protection purposes.
Specifically in the case of a thermoforming system, usually, a clamping frame is arranged at the forming station. Within the forming station, the clamping frame seals film with respect to the vacuum box. Thus, the size of the clamping frame usually defines the required size of the blank cut. In particular with regard to the length of the blank cut, it is therefore intended in practice not to unnecessarily exceed the length of the clamping frame in the machine direction.
The blank cut is placed in the transport means that is generally available in a thermoforming system. The transport means are formed in most cases by pairs of belts, usually chain-driven, with needles, clips or cards, or by other transport chains. The transport means holds the blank cut placed thereon on both sides at the film edges and transports it in this manner through the thermoforming system.
Since generally a heating station is available, and the thermoforming system as such effects in any case heat irradiation onto the film, the blank cut needs to be additionally held on the infeed and outfeed sides with cooled transverse clamping bars so as to avoid a concave necking which otherwise would occur due to the influence of heat.